This invention relates generally to the reduction of particulate material generation by workpiece handling components, and, more particularly to reduced generation of particles on workpiece handling components fabricated from metals or other materials and having a hard carbonaceous surface film.
Vacuum chucks are often used to hold and transport or otherwise handle workpieces such a semiconductor wafers, for example. Flat spatula-like holders called wafer picks are also used to transport semiconductor workpieces, with or without the benefit of vacuum assisted holding. In some other cases, electrostatic attraction is used to hold workpieces to chucks or picks for handling. When the workpieces are being chucked or unchucked or moved or transported by such chucks or picks, small relative motions between the handler (chuck or pick) and workpiece can result in abrasion or other forms of wear to either the handler surface or to the workpiece. This wear or abrasion results in the creation of particulate materials which are generally undesirable, as for example in the case of semiconductor processing, where deposition of such particles on the semiconductor wafers can result in reduced yield of the semiconductor manufacturing process. Wear and abrasion to the workpiece is also sometimes undesirable, as for example in the case of semiconductor processing, where scratches or other damage that occurs to the semiconductor workpiece surfaces can also result in reduced manufacturing yield or degraded performance of semiconductor devices.
It is has been found convenient to manufacture vacuum chucks and wafer picks from several types of metals, including for example, aluminum and various of the stainless steels. Other materials have also been used. Some prior art workpiece handlers have been made using metal chucks or picks having a softer polymer coating (fluoropolymer, for example) so as to reduce the tendency for the handler to wear or abrade the workpiece. A drawback of this approach has been that small, hard environmental particles may be transported to the polymer-coated surfaces of the handler by contaminated workpieces or by other unintentional means. Such particles may then become imbedded in the relatively soft polymer coating where they can then scratch, abrade, or otherwise wear on the workpiece surfaces. In other examples of prior art, handlers have been made of very hard materials such as certain ceramics, or hard crystalline materials like sapphire. In such cases, the hard handlers resist the imbedding of foreign particles, but must be very smooth so that the handlers themselves do not scratch or abrade the workpieces. Since it is costly to machine and smooth such hard materials, and since such materials are often brittle and thus too fragile for some types of service, they have not been economically practical in many cases. In still another example of prior art, metal vacuum chucks have been coated with hard coatings such as aluminum oxide, titanium nitride, or hard carbonaceous films sometimes referred to as diamond-like-carbon (DLC) films. It has been found that these hard film coated metal handlers have a tendency to scratch, abrade, or wear the workpieces, producing undesirable amounts of particles, and it has also been found that portions of the hard coatings tend to wear off of the vacuum chuck surfaces more quickly than desirable, resulting in increasing degrees of particle generation and thus, unsuitability for many applications.
It is therefore an object of this invention to provide a handler for contacting workpieces and having a DLC coating that has a reduced tendency to result in scratching, abrasion, or wear of the workpieces.
It is a further object of this invention to provide a handler for handling workpieces and having a DLC coating that resists being worn or otherwise separated from the handler.
It is a still further object of this invention to provide a handler for workpieces that has a reduced level of generation of particles when handling workpieces.
The objects set forth above as well as further and other objects and advantages of the present invention are achieved by the embodiments of the invention, described hereinbelow.
The present invention is a handler, which may be a vacuum chuck or a pick, for workpieces having a flat surface as is the case, for example, with most semiconductor wafers. The handler is fabricated from metal or other material so as to be of a desirable shape for holding a workpiece during manipulation, orientation, or transport. The holding function may be accomplished by gravity or vacuum assisted holding or other appropriate means including mechanical restraints or electrostatic attraction. In general the handler of the invention will have a surface for contacting a substantially flat surface on the workpiece, for example a side of a semiconductor wafer. The surface of the handler that is to contact the flat surface of the workpiece is made flat and smooth according to requirements and methods described hereinbelow and is coated with a DLC film or other hard coating, yielding an improved handler that is resistant to scratches, abrasion, and wear and that has a reduced tendency to scratch, abrade, or wear the workpiece, and that results in reduced generation of particles during the handling of the workpieces.
For a better understanding of the present invention, together with other and further objects thereof, reference is made to the accompanying drawings and detailed description and its scope will be pointed out in the appended claims.